Safe load indicator



Nov. 25, 1969 J. A. DELUCA, JR

SAFE LOAD INDICATOR 2 Sheets-Sheet l Filed Oct. 24. 1966 Nov. 25, 9999 J. A. DELUCA, JR 3,479,984

SAFE LOAD INDICATOR Filed Oct. 24, 1966 2 Sheets-Sheet 2 United States Patent 3,479,984 SAFE LOAD INDICATOR Joseph A. Deluca, Jr., 21 Maplewood Lane, Faulk Road, Wilmington, Del. 19803 Filed Oct. 24, 1966, Ser. No. 588,938 Int. Cl. G09f 9/40 U.S. Cl. 116124 2 Claims ABSTRACT OF THE DISCLOSURE Precise instrument for simultaneously indicating maximum safe load that can be lifted by crane at any inclination of crane boom relative to horizontal, radius of boom and boom angle comprises pendulum for producing motion in response to changes of crane boom angle. Instrument also includes pointer assembly and transmission for connecting pointer assembly to pendulum. Dial face is provided for particular crane, for particular length and type, boom and dial has safe load, boom radius, and boom angle readings for each working angle of that boom. Pointer assembly includes pointer arm that moves across dial face as boom angle changes to thereby simultaneously indicate consistently and exactly safe load, boom angle, and boom radius readings by position of pointer arm on dial face without gain or loss at any inclination of boom.

The present invention relates to an indicator and more particularly to a precise instrument for indicating the maximum safe load which can be lifted by a crane.

All lifting cranes have a safe load capacity which is in part determined by the angle of the crane boom relative to the horizontal, and the length of the boom. As the boom angle increases the effective radius of the boom decreases which in turn enables the crane to lift a greater load. In the past, several arrangements have been proposed for indicating the working angle of a crane boom, or in other words, the inclination of the boom relative to the horizontal. The measured boom angle together with appropriate crane charts usually located in the cab of the crane are then utilized to compute the load which can be safely lifted by the crane at that particular boom angle. Not only are the prior indicators inaccurate but these arrangements require a separate crane chart and the determination of safe load by the crane operator. As can readily be understood, the crane operator is generally preoccupied with the operation of the crane and thus, the safe load determination is usually computed in a hasty and often inaccurate manner. The prior inaccurate boom angle indicators coupled with the often inaccurate safe load computation has frequently caused serious problems in the eflicient operation of lifting cranes.

Accordingly, it is the object of the present invention to provide a highly accurate instrument for indicating the maximum safe load which can be lifted by a crane at any inclination of the crane boom relative to the horizontal.

Another object of the present invention is to provide a precise instrument for a crane which simultaneously in dicates safe load, boom radius and boom angle readings.

In accordance with the present invention a precise instrument is provided for accurately indicating the maximum safe load which can be lifted by a crane at any angle of the crane boom relative to the horizontal. An angle responsive motivating arrangement that may take the form of a pendulum, for example, can be provided for producing motion in response to changes of crane boom angle, and a transmission system operates to transmit motion from the motivating arrangement to a pointer assembly, As the motivating arrangement moves in response to angle changes of the crane boom a pointer arm moves across one of a series of dial faces to indicate the maxi 3,479,984 Patented Nov. 25, 1969 ICC mum safe load which can be lifted by the crane at any particular angle of the boom relative to the horizontal.

The series of dial faces includes a single dial face for each length of boom and each face is correlated to the boom length so that safe load, boom angle and boom radius readings are readily indicated at all working angles of the boom relative to the horizontal.

Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

FIGURE 1 is a pictorial view of a crane and an instrument according to the present invention;

FIGURE 2 is a front elevational view of an instrument according to the present invention;

FIGURE 3 is a side elevational view of the instrument shown in FIGURE 2 with parts broken away to show detail;

FIGURE 4 is a rear elevational view of the instrument shown in FIGURE 2 with parts broken away to show detail; and

FIGURE 5 is a diagrammatic perspective view of a pointer assembly and an arrangement for motivating that assembly.

Referring in more particularity to the drawings, FIG- URE 1 shows a crane 10 having a boom 12 pivoted to the body of the crane. Suitable cables 14 are provided for elevating the free end of the boom and for lifting a load fixed to the cable portion 16. at that end. An instrument 18 is attached to the boom at 20 so that the instrument is in full view of the crane operator at all working angles of the boom.

According to the present invention, the instrument 18 comprises an angle responsive motivating arrangement 22 for producting motion in response to angular changes of the boom relative to the horizontal. A transmission system 24 connects the angle responsive motivating arrangement 22 to a pointer assembly 26 so that movement of the motivating arrangement is transmitted to the pointer assembly, as explained more fully below. The pointer assembly cooperates with one of a series of readily removable dial faces, such as the dial face 28 illustrated in FIGURE 2, to indicate the maximum safe load which can be lifted by the crane at any boom angle.

The angle responsive motivating arrangement 22 of the present invention may take the form of a pendulum 30 fixed to a structural support plate 32 by a U-shaped bracket 34 secured to the back of the support plate by screws, for example. The pendulum 30 is secured to a transverse shaft 36 journaled in the opposite sides of the U-shaped bracket 34. As shown in FIGURE 4, the pendulum 30 has a yoke portion 38' and the transverse shaft 36 extends through that yoke portion. The shaft 36 also carries a pulley 40 disposed in the yoke portion 38 of the pendulum. This pulley forms part of the transmission system 24 so that swinging motion of the pendulum is ultimately transmitted to the pointer assembly 26 by the pulley 40 and the remainder of the transmission system.

As shown in FIGURES 3 and 4, one side of the U- shaped bracket 34 has a bumper 42 fixed thereto by an L-shaped plate 44. The bumper 42 functions to limit the movement of the pendulum, as shown in fantom in FIG- URE 3, by engaging the pendulum at one extreme of its swinging motion. Movement of the pendulum is also limited in the opposite direction by the bracket 34, this position also being shown in fantom in FIGURE 3.

The rear side of the structural support plate 32 carries an arrangement 46 for preventing swinging motion of the pendulum 30. This arrangement comprises a locking element 48 which can be moved into engagement with a knurled nut 50 at one end of the transverse shaft 36. Engagement of the locking element with the knurled nut prevents the shaft from rotating which in turn locks the pendulum in place. The locking arrangement 46 is employed to prevent swinging motion of the pendulum during shipment and calibration of the instrument, as explained more fully below.

The transmission system 24 of the present invention also includes a second transverse shaft 52 journaled in the sides of the U-shaped bracket 34. The shaft 52 carries an idler pulley 54 having a somewhat smaller diameter than the pulley 40 on the shaft 36. A cable 56 which may be constructed of prestressed stainless steel is trained about each of the pulleys 40, 54 and a third pulley 58 connected to the pointer assembly 26. Each of the pulleys may be dimensioned so that the swinging motion of the pendulum is increased by the transmission, such as a to 1 increase, for example. In order to obtain this particular increase the pulley 58 on the pointer assembly 26 is constructed so that its diameter is one-fifth the diameter of the pulley 40 of the transverse shaft 36.

As shown in FIGURE 5, the cable 56 has a suitable tensioner 60 which can take the form of a coil spring 62 connected at one end to the pulley 40, and at the other end to the cable. This arrangement assures proper tensioning of the cable under all environmental conditions of crane use. The motivating arrangement 22 and the transmission system 24 can also be enclosed by a casing 64 secured to the rear side of the structural support plate 32. A gasket 66 between the plate and easing may be provided for an airtight fit. As can readily be understood, the casing 64 protects the precise mechanisms enclosed therein from dirt, dust and water, for example.

The pointer assembly 26 includes a rotatable shaft 68 which as already mentioned carries the third pulley 58 of the transmission system 24. The shaft 68 extends through the structural support plate 32 and is journaled in that plate by a bushing 69. Bearings 70, 71 on the shaft 68 are provided for attaching it to the 'U-shaped bracket 34. The left-hand end of the shaft 68, as shown best in FIGURE 5, has a key 72 that forms part of a connection for securing a pointer arm 74 to the shaft. The pointer arm 74 in turn has an aperture 76 which enables the pointer to be positioned on the shaft 68 of the pointer assembly. A pair of internally threaded apertures 78 are provided, one on each side of the keyway, to secure the pointer arm tightly to the shaft, as explained more fully below. An indexing plate 80 having a keyway 82 also forms part of the connection for securing the pointer arm to the shaft 68. The plate 80 has a pair of arcuate slots 84 that register with the apertures 78 in the pointer arm when each of these elements is mounted on the shaft 68 of the pointer assembly. The plate 80 also carries a set screw 85 for anchoring the plate to the shaft, as explained below. Finally, a thin disc 86 is provided having a pair of spaced holes 88 that register with the arcuate slots 84 in the indexing plate 80 and the apertures 78 in the pointer arm 74.

According to the present invention, each dial face 28 of the dial face series has a central aperture 90 to enable the dial face to be positioned against the front side of the structural support plate 32, as shown in FIGURES 2 and 3. The shaft of the pointer assembly extends through the central aperture in the dial face and the pointer arm 74 is connected to the shaft, as explained above. The support plate 32 has a locating pin 92 that cooperates with an aperture 94 in each dial face. The central aperture 90 of the dial face 28 together with the locating aperture 92 function to accurately position the dial face at a predetermined location on the support'plate 32 of the instrument. The support plate 32 also carries a spring biased knockout pin 96 to facilitate removal of the dial face from the instrument and three spring-loaded swivel lugs 98. The lugs 98 engage the periphery of the dial to hold it in place on the structural support plate.

As described above, a dial face is provided for each boom length. Each face has three scales 100, 102, 104 so that three readings are simultaneously indicated for each position of the pointer arm 74 on the dial face. The major scale 100 is located adjacent the periphery of the dial and this scale gives safe load readings for any inclination of the boom relative to the horizontal. The scale 100 may be in pounds, for example, with the last three zero digits omitted for purposes of clarity and convenience. The two remaining scales 102, 104 enable the operator to determine the effective radius of the boom together with the boom angle.

As shown in FIGURE 2, the front portion of the instrument 18 comprises a housing 106 hinged to the structural support plate 32 by a hinge structure 108. The housing 106 has a transparent window portion 109 which can be constructed of glass or lucite, for example. Latches 110 may also be provided on the structural support plate 32 for locking the housing in a tightly closed position.

In operation, the instrument 18 according to the present invention operates to accurately indicate safe load, crane boom radius and crane boom angle for any length boom at any angle of that boom relative to the horizontal. The instrument 18 can be secured to the boom 12 of the crane 10 by a special bracket structure 112, as shown in FIGURES 1 and 3. Preferably, the structural support plate 32 is positioned in such a manner so that the dial face attached to that plate is in full view of the operator at all working angles of the boom. In most instances it is desirable to position the instrument on the boom so that the dial face is disposed in a plane 15 degrees to the longitudinal axis or center line 114 of the boom since this position enables the operator to readily read the dial at all working angles of the boom.

Once the instrument is positioned on the crane boom 12 by the special bracket structure 112 the appropriate dial face for that length boom is selected from the series of dial faces. The pointer arm 74 is first detached from the pointer shaft 68 to enable the crane operator to position the appropriate dial face against the structural support plate 32, the dial face being accurately positioned on the plate by the locating pin 92. After the lugs 98 are in their dial holding position the instrument is calibrated by first measuring the inclination of the boom 12 with another instrument, such as a mercury protractor, for example. The mercury protractor measures the true angle of the boom 12 along its longitudinal center line 114 and once this is accomplished the pendulum 30 is locked in place by the arrangement 46. This prevents swinging motion of the pendulum until the locking element 48 is moved away from the knurled nut 50* on the end of the transverse shaft 36. With the pendulum locked in place, the pointer arm 74 is then mounted on the pointer shaft 68 and rotated relative to the shaft so that the arm points to the approximate angle of the boom. Next, the indexing plate is positioned on the end of the shaft and the disc 86 secured to the pointer arm 74 by threading the locking screws 89 into the internally threaded apertures 78 in the pointer arm. Before the screws 89 are fully tightened the pointer arm is moved slightly to the exact angle reading measured by the mercury protractor. The set screw is then tightened to anchor the pointer arm 74, indexing plate 80 and disc 86 to the pointer shaft 68.

After the instrument is calibrated as described above, the locking element 46 is withdrawn from engagement with the knurled nut at the end of the transverse shaft 36 so that the pendulum 30 can swing in response to changes of the boom angle. The casing 64 is then secured to the rear side of the structural support plate 32. The particular arrangement for connecting the pointer arm to the shaft facilitates precise calibration of the instrument and after the hinged housing 106 is closed the instrument is ready for continuous and uninterrupted use.

Most crane booms have a 25 foot heel section pivoted to the body of the crane and add tional 5 and 10 foot sections are also provided for constructing various boom lengths. The heel section usually remains fixed to the crane and the other sections are added to the heel section to construct a boom having the desired length. The instrument, according to the present invention, is positioned on the heel section of the crane boom by the bracket structure 112, as explained above. When a difiierent length boom is desired the additional boom sections are fixed to the heel section to construct the new boom. Once the new bOOm is so constructed the instrument is adapted to the new boom length by first removing the pointer arm and the old dial face, and then positioning the appropriate dial face for the new boom against the structural support plate 32. Removal of the pointer arm is carried out easily by simply loosening the set screw 85 and then removing the assembled pointer arm 74, indexing plate 80, and disc 86 from the pointer shaft '68. After the new dial face is accurately positioned on the support plate 32, the pointer arm is returned to its position on the pointer shaft and the set screw 85 tightened to positively anchor the pointer arm to that shaft. Calibration of the instrument is unnecessary since he pointer arm returns to a position on the shaft that indicates the true boom angle. The key 72 on the shaft 68 and the keyway 82 in the indexing plate 80 function to position the pointer arm at the same location it was positioned at the time of pointer removal. The removed dial face is then returned for storage with the remaining dial faces of the series.

What is claimed is:

1. A precise instrument for simultaneously indicating the maximum safe load that can be lifted by a crane at any inclination of the crane boom relative to the horizontal, the radius of the boom and the angle of the boom, the instrument comprising a frame, a pendulum connected to the frame for producing swinging motion about an axis in response to changes of crane boom angle, a pointer assembly including a shaft journaled to the frame having an axis of rotation normal to the axis of the pendulum, transmission means connected between the pendulum and the shaft of the pointer assembly for transmitting motion to the pointer assembly shaft from the pendulum, the transmission means including a pulley connected to the pendulum to rotate with and in the same direction as the swing of the pendulum, the pulley being spaced from the pointer assembly shaft and co planar therewith, and a cable trained about the pulley and the pointer assembly shaft for rotating the shaft as the pendulum swings, a dial face for a particular length boom connected to the frame, the dial face having safe load, boom radius and boom angle readings for each working angle of the boom, the pointer assembly further including a pointer arm connected at one end of the pointer assembly shaft for movement across the dial face as the boom angle changes whereby safe load, boom angle and boom radius readings are simultaneously indicated by the position of the pointer arm on the dial face at any inclination of the boom.

2. A precise instrument as in claim 1 wherein the pointer assembly shaft has a key at the end thereof to which the pointer arm is connected, an indexing plate with a keyway therein constructed and arranged to fit on the key end of the pointer assembly shaft, fastening means for connecting the indexing plate to the pointer arm, and securing means for releasably connecting the indexing plate and the pointer arm to the pointer assembly shaft whereby the indexing plate and the pointer arm may be removed as a unit from the pointer assembly shaft by loosening the securing means and the pointer arm is returned to its exact position on the pointer assembly shaft which position is determined by mating engagement of the key on the end of the pointer assembly shaft and the keyway in the indexing plate.

References Cited UNITED STATES PATENTS 1,857,172 5/1932 Wagner 340267 2,750,917 6/1956 Milligan 116-130 3,130,705 4/1964 Ingham 116136.5 3,250,996 5/1966 Fleetman 116114 XR 2,276,153 3/1942 Burnham et al. 33215.3 2,374,298 4/ 1945 Nasset 116124 2,418,593 4/1947 Martin et al. 116-124 3,012,537 12/1961 Thiel 1l6124 3,132,627 5/1964 Tiesatz 116124 FOREIGN PATENTS 10,709 1908 Great Britain.

LOUIS J. CAPOZI, Primary Examiner 

